Import patches-unapplied version 1.18.3-0ubuntu1 to ubuntu/xenial-proposed

Imported using git-ubuntu import.

Changelog parent: 2ae3aa2085cf3e4931018b7ed35a56be01c05a42

New changelog entries:
* New upstream release:
- Fix error that caused stdin to be closed. This seems to have lots of bad
side effects (greeter not working correctly, multi-seat failing).
- Add support for greeters running inside sessions. This is enabled by
setting X-LightDM-Allow-Greeter inside the session .desktop file.
The session can then use liblightdm to connect one greeter to the
daemon. The communication is done using a socket
(/var/run/lightdm/<user>/greeter-socket) that is accessible to any
process run by that user. Consider controlling access to this socket
using a MAC system such as AppArmor. (LP: #1582242)
- Fix various memory management issues exposed by the use of in-session
greeters.
* debian/patches/lp1605117.patch:
- Applied upstream

New changelog entries:
* New upstream release:
- Fix error that caused stdin to be closed. This seems to have lots of bad
side effects (greeter not working correctly, multi-seat failing).
- Add support for greeters running inside sessions. This is enabled by
setting X-LightDM-Allow-Greeter inside the session .desktop file.
The session can then use liblightdm to connect one greeter to the
daemon. The communication is done using a socket
(/var/run/lightdm/<user>/greeter-socket) that is accessible to any
process run by that user. Consider controlling access to this socket
using a MAC system such as AppArmor. (LP: #1582242)
- Fix various memory management issues exposed by the use of in-session
greeters.
* debian/patches/lp1605117.patch:
- Applied upstream